The invention relates to a process and an arrangement for producing spools containing two yarn components respectively and serving as feed spools for a twisting process, these two yarn components being drawn by means of adjacent drafting frames of a joint machine, then being prestrengthened by means of pneumatic false-twisting nozzles, and subsequently being cross-wound onto a spool.
In the case of a process and an arrangement of the initially mentioned type (German Patent Application No. P 36 06 932.9 corresponding to my commonly owned pending United States patent application Ser. No. 013,798 filed Feb. 12, 1987) the two yarn components are each drawn to the desired size in the drafting frames. Subsequently, they are prestrengthened in false-twisting nozzles, in which case this prestrengthening is carried out only to such an extent that the two yarn components together have a sufficient strength in order to be wound up and then be subjected to a subsequent twisting process. During this prestrengthening, the yarn components are not provided with a true twist. By means of the false twist, the yarn components are prestrengthened in such a way that, when the false twist is undone, several spread-away fiber ends are wound around the essentially untwisted fiber core. During the subsequent twisting, therefore practically no twist must be undone, so that the prestrengthening by pneumatic false-twisting as well as the subsequent twisting may each be carried out at very high production speeds. In the case of this arrangement, the drafting frames and the false-twisting nozzles are arranged in such a way that the same yarn-moving paths are obtained for both yarn components to the spool onto which they are cross-wound.
Even if the drafting frames are designed as well as possible, defective drafts will still occur occasionally. Since the two jointly wound-up yarn components have drafting frames with joint bottom cylinders and, as a rule, are also equipped with top rollers that are combined to pressure roller duos, the danger exists that defective drafts of this type occur simultaneously at both yarn components. These defective drafts will then be doubled in the double yarn and may have a disadvantageous effect.
An objective of the invention is to develop a process and an arrangement of the initially mentioned type in such a way that an occurrence of defective drafts does not result in more serious defects in the finished yarn.
This objective is achieved by guiding the two yarn components between the drafting frames and the spool on paths of a different length.
As a result, it is achieved that in the drafting frames thick or thin points produced simultaneously in both yarn components are not located directly next to one another in the later-formed double yarn, but at a distance in moving direction of the yarn that is determined by the paths of different lengths. Thus, the quality can be improved of a twist-type finished product that is produced from the double yarn.
In the case of a preferred arrangement for achieving this objective, it is provided that, between the drafting frames and the devices for the winding-up of two yarn components, at least for one of the yarn components, guiding elements are provided that determine yarn paths of different lengths for the two yarn components. In the case of a first embodiment, it is provided in this case that the false-twisting nozzles extend toward one another at an acute angle in moving direction of the yarn, and that guiding elements are arranged between the drafting frames and a withdrawal device that is common for both yarn components. In the case of another embodiment, it is provided that, between the common devices for the winding-up of the two yarn components and the respectively separate withdrawal devices, guiding elements are arranged for at least one of the yarn components.
In a further embodiment of the invention, it is provided that the wind-up device for the common spool is arranged as a straight-line extension of the drafting frame and of the pertaining false-twisting nozzle of one yarn component, and that the guiding elements are assigned to the other yarn component. As a result, a slightly asymmetrical arrangement is obtained which, however, implements the different yarn moving paths in a simple way.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.